<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style>
			p{
				float: left;
			}
			.abc{
				width: 100%;
				background-color: aqua;
			}
		</style>
	</head>
	<body>
		<div class="abc">
		 <p>123</p>
		 <p>456</p>
		 <div style="clear: both;"></div>
		</div>
	</body>
</html>